Molecular phylogeny and taxonomy of the genus Vernaya (Mammalia: Rodentia: Muridae) with the description of two new species

Abstract The climbing mouse is a rare, small mammal listed as an endangered species on the China species red list. Molecular phylogenetic analyses and the evolutionary history of the genus remain unexplored because of the extreme difficulty in capturing individuals and their narrow distribution. Here, we collected 44 specimens, sequenced one mitochondrial and eight nuclear genes, and integrated morphological approaches to estimate phylogenetic relationships, delimit species boundaries, and explore evolutionary history. Molecular analyses and morphological results supported the validity of these four species. Here, we describe two new species, Vernaya meiguites sp. nov. and Vernaya nushanensis sp. nov., and recognize Vernaya foramena, previously considered a subspecies of Vernaya fulva, as a valid species. The estimated divergence time suggests that the climbing mouse began to diversify during the Pliocene (3.36 Ma).


| INTRODUC TI ON
Southwestern China has an extremely unique and complex topographic structure with high species richness.He and Jiang (2014) detailed the phylogeographic structure of sky islands in southwestern China, revealing the factors influencing species evolution and the general pattern of allopatric speciation.The number of species in China has markedly increased in recent years, mainly because of the discovery of new species (Jiang et al., 2015;Wilson & Reeder, 2005).New species of small mammals have been frequently reported in southwestern China (Chen et al., 2017;Liu et al., 2019;Pu et al., 2022), indicating that species diversity remains underestimated.Some unsystematically studied species require further classification and revision (Chen et al., 2017).
Vernaya is a monotypic genus belonging to the subfamily Murinae of the family Muridae, in the order Rodentia (Musser, 1979;Musser & Carleton, 2005).It is distributed in the mountainous areas of southwestern China (western Yunnan, central and northern Sichuan, southern Gansu, and southwestern Shaanxi) and extends to northern Myanmar (Allen, 1927;Anthony, 1941;Li & Wang, 1995;Musser & Carleton, 2005;Smith et al., 2008;Wang et al., 1980).Vernaya fulva was first collected in Lanping, Yunnan, in 1916 by Andrews and Heller.In 1927, Allen characterized it as a member of the genus Chiropodomys and named it Chiropodomys fulvus.After several revisions, it was finally named Vernaya, and the species name was changed from fulvus to fulva (Allen, 1927;Anthony, 1941;Lunde, 2007).
A group of specimens from Wanglang, Sichuan, was identified as the new species, Vernaya foramena (Wang et al., 1980).
Subsequently, Li and Wang (1995) considered V. foramena to be a geographic subspecies of V. fulva (Li & Wang, 1995), namely V. f. foramena.This arrangement has been followed in many subsequent studies (Lunde, 2007;Smith et al., 2008;Wang, 2003;Wei et al., 2021;Wilson et al., 2018).In addition, the remnants of V. fulva and four extinct species from the same genus were found in late Pleistocene cave sediments in the Sichuan-Guizhou region of southern China (Zheng, 1993).Vernaya fulva is the only extant species in the genus and is listed as endangered (EN) on the China species red list (Jiang et al., 2021).According to the International Union for Conservation of Nature (IUCN) Red List Categories (Aplin, 2017), Vernaya fulva belongs to the category of "Least Concern."However, the molecular systematics and evolutionary history of this genus have not yet been studied.Whether V. f. foramena can be considered an independent, valid species has not yet been analyzed from a systematic molecular perspective.In this study, we collected 44 specimens of the genus Vernaya from Sichuan, Chongqing, and Yunnan provinces in China.Morphological characteristics, principal component analysis of skulls, and mitochondrial and nuclear genes were used to (1) determine whether V. f. foramena is an independent valid species, (2) infer the phylogenetic relationships of the genus Vernaya, and (3) explore the evolutionary history of the genus Vernaya.

| Molecular data and analyses
From 1979 to 2022, 44 Vernaya specimens from Sichuan, Chongqing, and Yunnan provinces in China were collected using snap traps (Figure 1 and Table 1).All samples were numbered, and their morphological data [including head-body length (HBL), tail length (TL), ear length (EL), and hind foot length (HFL)] were measured.Fresh liver or muscle tissues were collected from 20 individuals and stored in 99% pure analytical ethanol.After returning to the laboratory, the tissue samples were stored at −80°C after changing the analytical alcohol for molecular studies.All individuals were made into the study skins.
Tissues and specimens used in this study were stored at the Sichuan Academy of Forestry (SAF), College of Life Sciences of Sichuan Normal University (SCNU), Kunming Institute of Zoology (KIZ), and College of Life Sciences of Sichuan University (SCU) (Table 1).
Total DNA was extracted using an Animal Tissue Genomic DNA Rapid Extraction Kit (Chengdu Fuji Biotechnology Co., Ltd.).The primers used for PCR amplification are shown in the Table S1.PCR conditions consisted of an initial denaturing step at 94°C for 5 min, followed by 35 cycles of 45 s denaturation at 94°C, 45 s annealing at 49-60°C, 90 s extension at 72°C, and a final extension step at 72°C for 10 min.561 bp], which are good genetic markers for determining the phylogenetic relationships of some mammals (He et al., 2017;Meredith et al., 2011).Sequencing was performed by Beijing Tsingke Biotech Co. Ltd.The original sequences were obtained via comparison using Mega 5.0 (Tamura et al., 2011), supplemented by manual correction, splicing, and confirmation of the normal translation of all sequences.
The sequence data of the outgroups (Mastomys coucha, Mus musculus, and Rattus norvegicus) were downloaded from GenBank (Table S2).
Phylogenetic analyses were conducted using the following three datasets: a mitochondrial dataset (CYTB), an all-gene combined dataset (mtDNA + nuDNA), and an all-nuclear gene dataset (nuDNA).
We used jModelTest 2.1.7(Darriba et al., 2012) to detect the optimal model for each gene.The fitness of the model was evaluated using the Akaike Information Criterion (Luo et al., 2010), and the best model for each gene is shown in Table S1.
Bayesian tree reconstruction was performed using BEAST v1.7 (Drummond et al., 2012), and each analysis consisted of 100 million generations, which were sampled every 5000th generation.The relaxed uncorrelated lognormal clock model and Yule species formation model were used for each operation.Statistics were performed using Tracer v1.6 (Rambaut & Drummond, 2013) to confirm that the effective sample sizes (ESSs) were greater than 200.The first 10% of the trees were discarded as burn-in using TreeAnnotator v1.6.1.We used Figtree v1.4.3 (Rambaut, 2016) to perform the output of the phylogenetic tree, and posterior probabilities (PP) >.95 were considered to be strongly supported (Huelsenbeck & Rannala, 2004).
Genetic distances were calculated based on the CYTB gene using the Kimura two-Parameter (K2P) model (Kimura, 1980) in Mega 5.0 (Tamura et al., 2011), with 1000 bootstrap replications.Species were identified using a monothreshold GMYC model based on a maximum genealogical confidence tree of mitochondrial genes (Pons et al., 2006).The GMYC analysis was performed using the time-calibrated gene tree as the input tree derived from the mitochondrial dataset without outgroups, and the split package was applied to the R environment for species delimitation (Paradis et al., 2004).
To verify the genetic differentiation detected in the genus Vernaya, the gene tree constructed in the previous step was used as a guide tree, and BPP v3.1 (Yang & Rannala, 2010) was used to test the independent evolutionary lineage hypothesis of these populations under multi-species fusion (Yang & Rannala, 2010).Datasets 2 (mtDNA + nuDNA) and 3 (nuDNA) were included in the analysis.
Algorithms 0 and 1 were used to specify the rjMCMC moves between the different species-partitioning models.We set the size and divergence time of the ancestral population using two prior settings: (1) a relatively large ancestral population and shallow branches [G (1, 10) for θ and G (2, 2000) for τ]; and (2) a relatively small ancestral population and shallow branches [G (2, 2000) for θ and G (2,2000) for τ].Each rjMCMC was run for 100,000 generations and sampled for each 100a generation after discarding 10,000 generations as pre burn-in.If the posterior probability was greater than .95,each clade was considered an independent species.Divergence time was estimated on the nuDNA dataset, which was analyzed in BEAST v1.7 (Drummond et al., 2012).Two fossil calibration points were used to evaluate the divergence time for the group.All fossil calibration age constraints were treated as log-normal distributions (Ho, 2007).(1) The split of Mus and Rattus was approximately 15.9 Ma (upper 95%, 15.9-16.41Ma) (He et al., 2019).( 2 Yunlong, Yunnan 99.11484 25.75724 2500 ZHAO et al. (Jacobs & Pilbeam, 1980;Lundrigan et al., 2002) indicated a minimum difference of 5.7 Ma (upper 95%, Ma) between different house mouse lineages.The BEAST analysis used a Yule tree prior and a relaxed lognormal clock model.Each analysis ran for 100 million generations and was sampled every 5000th generation.
The posterior distribution and ESS of each parameter higher than 200 were calculated in Tracer v1.6 (Rambaut & Drummond, 2013).
TreeAannotator v1.6.1, which was set to the first 10% of the generations, was used to determine the necessary burn-in fraction.

| Morphological data and analyses
The external measurement data for the specimens were obtained from the specimen labels.Skull measurements followed those of Liu et al. (2007Liu et al. ( , 2012) ) and Patton and Conroy (2017) The specimens of the measured species of Vernaya are shown in the Table S3.The measured data were analyzed using SPSS (version 20.0) for correlation.The overall similarity between species was evaluated using principal component analysis (PCA), under the condition that all data satisfied a normal distribution.A discriminant analysis was performed to determine whether the classification of the specimens was accurate.
We recorded the morphological characteristics of the male genitalia (Hooper, 1958), prepared the glans penis using standard methods (Hooper, 1958;Lidicker, 1968), and characterized the bacula structures (Yang & Fang, 1988).The glans were preserved in 75% ethanol.Dissection was performed using a binocular microscope, and the morphologies of the urethral lappet, dorsal papilla, and outer crater papilla were observed and described.The bacula were prepared according to the established methods (Liu et al., 2007(Liu et al., , 2012)).
Morphologies of the proximal, distal, and lateral baculae were observed under a binocular dissecting microscope.

| Molecular results
CYTB for all individuals and nuclear genes for all individuals except the BDNF gene (two individuals) and ATP7A gene (three individuals) were obtained in this study, that is, 1140 bp for CYTB and 5575 bp for nuDNA.New sequence information was deposited in GenBank (Accession Numbers OR282742-OR282761, OR333541-OR333696, Table S2).BEAST was used to reconstruct phylogenetic relationships based on the three datasets, and the topologies obtained were approximately the same (Figure 2 occur in the Pliocene (Figure 3).
The K2P genetic distance of the CYTB gene between the four putative Vernaya species was calculated.The results showed that the genetic distance ranged from 0.078 to 0.144 (Table 2).The genetic distance between V. sp2 and V. foramena was 14.4%, followed by 12.7% between V. sp2 and V. fulva.The minimum genetic distance occurred between V. fulva and V. sp1 and was found to be 7.8%.Genetic distances among all species showed good species-level differences.The species delimitation results for the GMYC and BPP were identical.GMYC results divided the groups into four putative species (Figure S1).The BPP results are shown in Table S4, and the results of both datasets support four putative species.

| Morphological results
Eleven cranial measurements and four appearance traits were obtained for the four putative species (Table S3).The resulting value of the Kaiser-Meyer-Olkin measure of sampling adequacy (KMO) = 0.837 (Bartlett's test < 0.001) indicated that the data were suitable for PCA.The first two PCs, which explained 76.97% of the variance (Table 3), were selected to analyze Vernaya.The explanatory degree of PC1 was the highest at 59.87%, and all factor loadings were positive.The factor loadings of the UTL, PL, and SBL were >0.9.
Factor loadings >0.8 included GLS and BUM (Table 3); the explanatory degree of PC2 was 17.10% and was negatively correlated with LTL, ML, LUM, and LLM (loadings <−0.2).All other loadings were >0.02 (Table 3).The scatterplots showed that some individuals of different species partially overlapped and still exhibited a good separation trend (Figure 4a).The variation in V. foramena was large, mainly distributed in the negative region of PC2 (Figure 4a), whereas most of V. fulva was distributed in the positive region, indicating that the skull was large and the braincase was wide.Most of V. sp1 occurs along the positive region of PC1 and the negative region of PC2 (Figure 4a), indicating that it has a relatively large skull and small braincase.V. sp2 was distributed in the positive region of PC2 and negative region of PC1 (Figure 4a), but only for reference owing to the small number of specimens.
The results of the discriminant analysis showed that 92% of the specimens were accurately classified.Except for one individual of  V. foramena that was assigned to V. fulva and one individual of V. fulva that was assigned to V. foramena (Table S5), all four putative species could be clearly distinguished (Figure 4b).

Comparisons of the morphology and measurements among
the different taxa of the four putative species are summarized in Tables 4 and 5, Table S3, and Figures 5 and 6.A morphological comparison of the penises is presented in Table 6 and Figure 7.The different species had distinct tail types (Figure 5).The tails of V. foramena, V. fulva, and V. sp1 are all covered with dense and long hairs (Figure 5a4,b4,c4), among which V. foramena has brownish yellow hairs and the dorsal and ventral uniformity (Figure 5a4); V. fulva has black hair and the ventral part is visibly lighter than the dorsal part (Figure 5b4); V. sp1, the hair on the back of the tail is yellow from the base to two-thirds of the tail, black from one-third of the tail, spindle-shaped dense hair clusters formed at the tail, and yellow hair on the ventral (Figure 5c4).V. sp2 was covered with short and sparse hair and was gray (Figure 5d4).
Vernaya foramena was the smallest of the four species (average HBL = 63 mm, average TL = 112 mm, average HBL > 67 mm, and average TL > 124 mm).The HBL of V. sp2 was the longest (average HBL/ TL = 0.57), the relative size of the skull was the smallest (average GLS = 20.62 mm) (Table 4), and the skull of V. sp1 was the largest.
Dental features are less variable in this genus.The tooth formula is 1.0.0.3/1.0.0.3.The length of the first upper molar was approximately equal to the sum of the second and third upper molars (Figure 6).M 1 and M 2 had three transverse ridges.Except for the first transverse ridge of M 2 , the remaining transverse ridges had three longitudinal tooth cups.The third transverse ridge of M 1 and M 2 had an additional transverse ridge, and M 3 had two plate transverses (Figure 6).Among them, the tooth characteristics of V. foramena alone showed some variations compared to those of other species: (1) The tooth cups of the second and third transverse ridges of V. foramena were notably degenerated and tended to be plate-like transverse ridges (Figure 6a2), whereas the others were distinctive, with the central tooth process being the largest, followed by the lateral dentition (Figure 6b2,c2,d3).
(2) The difference between the two mandibular teeth was that the two accessory processes of V. foramena were connected (Figure 5a7) [except for one specimen (SAF201560)], whereas the accessory processes of the other were separated (Figure 5b7,c7,d7).The dental characteristics of V. sp1 and V. sp2 were consistent with those of V. fulva; no substantial variations were observed.
The penises of the four species differ significantly.The dorsal area of the outer crater of V. foramena was concave (Figure 7a).The lateral and distal bacula were cartilaginous, the proximal baculum was a robust bone, and the base was diamond shaped.The urethral (Figure 7a2) and dorsal papillae (Figure 7a3) were short and thin, respectively.The outer  carter of V. fulva was divided into two petals (Figure 7b); the lateral and distal bacula were cartilaginous; the proximal baculum was thin bone and the base rhombic; the dorsal papilla (Figure 7b3) was longer and sturdier than V. foramena; and the urethral papilla (Figure 7b2) was extremely short and bean-like.The dorsal outer crater of V. sp1 was slightly concave, the inner crater was visible, the lateral and distal bacula were cartilaginous, the proximal baculum was a robust bone, and the base was solder-tipped.The dorsal papilla (Figure 7c3) was long and sturdy, resembling V. fulva, and the urethral papilla (Figure 7c2) was extremely short and bean-like.The dorsal outer crater of V. sp2 was circular, not concave; the lateral, distal, and proximal bacula were bone; however, the lateral bacula was only slightly ossified, and the distal and base parts of the proximal baculum were semi-circular.The dorsal papilla (Figure 7d3) was long and sturdy, and the urethral papilla (Figure 7d2) was very thin and relatively long.

| DISCUSS ION
In 1980, Wang et al. (1980) proposed that V. foramena was a new species of the genus Vernaya (Wang et al., 1980).He suggested that the distinguishing features between V. foramena and V. fulva were mainly based on two points: (1) The frontal foramen ovale of V. foramena were clearly exposed and arranged in parallel, whereas the foramen ovale of V. fulva were hidden under a thin film and arranged in an "eight" shape.
(2) The two cusps of the additional transverse ridge of the posterior margin of the mandibular M 1 of V. foramena were connected, whereas those of V. fulva were separated.Later, Li and Wang (1995)  locations.They concluded that, in addition to the visible difference in hair color between V. foramena and V. fulva, the presence of the frontal foramen ovale and whether the two tooth tips of the additional transverse ridge of the M 1 posterior edge were connected vary from individual to individual.
According to our results, nearly half of the frontal foramen ovale in V. foramena was not exposed, whereas two in V. fulva were exposed.Therefore, we agree with Li and Wang (1995) that exposure to the foramen ovale differs between individuals.In addition, the connection or separation of the two dentary tips of the additional transverse ridges of M 1 distinguishes V. fulva from V. foramena.
The evolution of animals was closely related to the climate.
Research has shown that the diversity of rodents exhibited notable alterations with ancient climate change (Li et al., 2022).The apparent alteration of Pleistocene climates may have contributed to the expansion and divergence of the species (Song et al., 2013;Tagliacozzo et al., 2016;Xing et al., 2013).According to our analysis, the origin of species within the genus Vernaya can be traced back to the middle Pliocene, with species differentiation mainly occurring during the Pleistocene (V.foramena diverged from V. fulva and V. sp1 2.49 Ma, 95% CI = 0.8-6.23,and V. fulva and V. sp1 diverged 1.57Ma, 95% CI = 0.47-3.99).We speculate that this was related to climate change during the Pleistocene.The species formation and evolution of the genus Vernaya were closely related to the uplift of the Qinghai-Tibetan Plateau (QTP) and its biological characteristics.The QTP uplifted several times; the most intense one was during the Qinghai-Tibet movement (uplifting from 3.4 Ma, strong uplifting from 2.5 to 1.7 Ma) and the Kun-Huang Movement (1.2-0.6 Ma) (An et al., 2001;Shi et al., 1999;Zheng et al., 2000).This movement has changed the surrounding climatic patterns and topographic structures, providing strong support for the formation, distribution, and dispersal of species, and has shaped modern biodiversity.The earliest divergence of the genus can be traced back to 3.36 million years, and the subsequent divergence of several species occurred in 2.49 Ma (V.foramena) and 1.57Ma (V.fulva and V. sp1), respectively.These temporal events almost coincided with the uplift periods of the Tibetan Plateau.Thus, we hypothesized that the formation of these four species was caused by the overall uplift of the QTP, resulting in geographic isolation and the prevention of genetic exchange.Its small individual size, arboreal living habits, and weak diffusion ability further hinder gene exchange and the formation of new species.

| TA XONOMIC ACCOUNT
Historically, the genus Vernaya has been considered monotypic.In Diagnosis: HBL averages approximately half of the TL (slightly shorter than or slightly longer than half of the TL).Body light brownish yellow, entire dorsal tail covered with black hairs, ventral part notably lighter than dorsal part to distinguish it from congeners (Figure 5b4).
Remarks: A medium-sized species of Vernaya.Allen (1927) collected a specimen named Chiropodomys fulvus, which was later considered synonymous with Vandeleuria dumeticola (Allen, 1940).Anthony (1941) changed the name of the species to Vernaya fulva.
At present, this species is found in Yunnan Province alone and forms two groups with the neighboring V. nushanensis sp.nov.We speculate that communication is blocked by rivers, which leads to population differentiation.Geographical distribution must be determined by expanding the number of sampling points.
Distribution: Vernaya fulva is distributed in western Yunnan (Allen, 1927), China, west of the Lancang River (upper Mekong River in China), and extends into northern Myanmar (Anthony, 1941).The specimens were collected between 2100 and 3300 m.
Tissue samples from 20 climbing mice were amplified, sequenced, and analyzed.We sequenced one mitochondrial gene (CYTB, 1140 bp) for all samples and eight nuclear genes (recombination activating 1 [RAG1, 1080 bp]), including inverted-repeat-binding protein [IRBP, 1142 bp], growth hormone receptor [GHR, 748 bp], adenosine A3 receptor [ADORA3, 342 bp], administered beta 2 [ADRB2, 802 bp], amyloid beta precursor protein [APP, 296 bp], adenosine triphosphate 7a [ATP7A, 604 bp], and brain-derived neurotrophic factor [BDNF, ) The first fossil record of the genus Mus auctor F I G U R E 1 Map of the collection sites of the genus Vernaya in this study.TA B L E 1 Information on the collection sites of Vernaya specimens in this study.
) (Mastomys coucha, Mus musculus, and Rattus norvegicus were used as outgroups).This topology strongly supports the division of the genus Vernaya into four clades.Clade A, representing V. sp2, was monophyletic and consistently placed as the most basal lineage in the three datasets (all pp = 1.0).Vernaya sp1 (clade B) was classified as the sister branch of V. fulva (clade C).The branches of clades B and C were sister groups to clade D of V. foramena (Figure2).According to BEAST v1.7, the topological structure of the divergence time tree was the same as that of the nuDNA gene tree.The results showed that the latest common ancestor of Vernaya can be traced back to the Pliocene (3.36 Ma, 95% CI = 1.07-8.63),which is also the time when V. sp2 diverged from other species.Both the divergence time of clade B and C (2.49 Ma, 95% CI = 0.8-6.23)and the divergence time of V. sp1 and V. fulva (1.57Ma, 95% CI = 0.47-3.99)

F
Divergence times were estimated using BEAST based on a nuDNA dataset.Branch lengths represent time.Numbers left of the dash indicate posterior probabilities (PP), numbers right of the dash represent the median divergence time, and numbers within parentheses indicate the confidence interval.The two red asterisks indicate fossil-calibrated nodes.TA B L E 2 Kimura two-parameters (K2P) genetic distances in the genus Vernaya based on the CYTB gene.

F
Principal component analysis (PCA) based on skull measurement data of genus Vernaya (a) results of PCA and (b) canonical discriminant analysis of Vernaya.

Family
this study, we conducted a comprehensive reassessment of species diversity within the Vernaya genus by integrating molecular and morphological data.The results revealed a significant underestimation of the species diversity in the genus prior to this study.Based on these results, a thorough taxonomic revision of Vernaya species was performed.In summary, four species are currently recognized within the genus, the first being V. fulva, which was collected from TA B L E 5 Morphology comparison of genus Vernaya.long and dense; the ventral part is lighter than the dorsal part Brown-yellow hairs, long and dense, the dorsal and abdominal uniformity The hair on the back of the tail is yellow from the base to two-thirds of the tail, black from one-third of the tail, spindle-shaped dense hair clusters formed at the tail, and yellow hair on the abdomen Short and sparse hairs, The tooth protrusions of the second and third transverse ridges are distinctive The tooth protrusions of the second and third transverse ridges are obviously degenerated, especially the central tooth process The tooth protrusions of the second and third transverse ridges are distinctive The tooth protrusions of the second and third transverse ridges are distinctive 1st lower molar The two cusps of the additional transverse ridges are separated The two cusps of the additional transverse ridges are connected (most of specimens) The two cusps of the additional transverse ridges are separated The two cusps of the additional transverse ridges are separated areas east of the Nujiang River in Yunnan Province.The second most common species was V. foramena, which was previously considered a subspecies of V. fulva.However, our collection of specimens from the type locality of V. foramena revealed characteristics that differentiate it from V. fulva.Therefore, V. foramena should be recognized as a separate, valid species.In terms of morphological and molecular differences, individuals collected from the Meigu and Gongga Mountains in Sichuan were identified as a new species, designated V. meiguites.Additionally, specimens obtained from regions west of the Nujiang River in Yunnan were categorized as a novel species, referred to as V. nushanensis.This taxonomic update contributes to a better understanding of the diversity and evolutionary history of the Vernaya.Specimen number: 43989, an adult female collected by R. C. Andrews and E. Heller in 1916.The specimen was deposited at the American Museum of Natural History.Type locality: Yinpankai, Mekong River, western Yunnan, China, 9000 feet altitude.Common names: Climbing mouse, 攀鼠 (Panshu).

Holotype:
Specimen number: 75003, adult female collected in 1975.The specimen was deposited at China West Normal University.Type locality: Wanglang, Pingwu, Sichuan Province, China (2490 m a.s.l.).Common names: Apparent climbing mouse, 显孔攀鼠 (Xiankong Panshu).Diagnosis: Vernaya foramena is the smallest species in the genus Vernaya.The body is brown, the abdomen is white, and the hair base is gray.It is distinguished from other species based on the following features: (1) the tail is covered with long and dense brownish-yellow hairs; (2) the cusps of the second and third transverse ridges of the second upper molars are visibly reduced, especially the central cusp; and (3) the two cusps of the additional transverse ridges of the first lower molars are connected (Figure 5a1-a4 and 6a1-a8).

Etymology:
The new species is named after its type locality, Meigu County, where the Meigu Dafengding National Nature Reserve is located.This area is in the transitional zone between the Sichuan Basin and the Yunnan-Guizhou Plateau, the southeastern edge of the Qinghai-Tibet Plateau, and the middle of the Hengduan Mountains.The mountainous area of southwestern China is one of the key areas of global biodiversity and one of the most complete areas of subtropical mountain flora and fauna resources in southwestern China.Naming new species at the county level reflects the high value of biodiversity conservation.Thus, we suggest "Meigu climbing mouse" as the English common name and "美姑攀鼠 (Meigu Panshu)" as the Chinese common name.
Factor loadings and percentage of variance explained for principal component analysis.
The average and standard deviation of the measurement data of the appearance and skull morphology of the specimens of the genus Vernaya used in this study.
compared specimens from Zhouqu County in Gansu and Fengxian in Shaanxi and found that the two discriminatory characteristics mentioned by Wang were unstable in specimens from different TA B L E 4